Fishy question~!?

I am just curious as to why fish sit at the top of the tank? I had a few that will just sit there in a corner, if u put ur hand in there they swim away from it etc then sometimes they swim around the tank. Is it lack of oxygen or something? anyone know? dont want my fishies dieing over something stupid

I was thinking in intimidation as well. I had a Percula clown do it. I just added a blue regal to smaller tank with a tomato clown and he was sittin at the top as well, so i stuck my hand in there and got him to move a lil, seems to be doing better. Didnt kno if it had n e thing to do with the tank needing aeration or some other suppliment.